Aramid polymer from aromatic dicarboxylic acid mixture and aromatic diamine mixture

ABSTRACT

Copolyamides are described comprising: (1) 0.22-0.28 mole fraction units derived from terephthalic acid; (2) 0.2-0.28 mole fraction units derived from paraphenylene diamine; (3) 0.22-0.28 mole fraction units derived from isophthalic acid; and (4) 0.22-0.28 mole fraction units derived from a 3,3&#39;- or 4,4&#39;-diamine of diphenyl methane, diphenylpropane-2,2, diphenyl cyclohexane-1,1, diphenyl ether, diphenyl sulfide, diphenyl sulphone, or benzophenone.

This is a division of application Ser. No. 245,231, filed Sept. 16,1988, now U.S. Pat. No. 4,908,264.

The invention relates to composites comprising an aramid matrix andreinforcing fibres embedded therein, to the preparation thereof fromsuitable semi-manufactured products, and to particular aromaticcopolyamides.

It is known to incorporate long fibres, for instance in the form offabrics, as a reinforcement in a thermoplastic matrix by impregnatingthe fabrics with a melt of the thermoplastic material. The resultingsemimanufacture can be compression moulded into shaped articles butdisplays the disadvantage of being rigid. Handling and processingthereof give rise to difficulties. It has therefore been proposed beforethat a flexible structure be prepared from various types of fibres, atleast one type of fibre being thermoplastic and the other fibre beingmaintained as fibre during the melting of the first fibre under theconditions of compression moulding. Such a combination of reinforcingfibres and thermoplastic fibres has the advantage that it forms aflexible semi-manufactured product, so that it can readily be broughtinto any desired shape. Subsequent use of elevated temperature andpressure will cause the thermoplastic fibres to melt, as a result ofwhich the thermoplastic material will penetrate between the reinforcingfibres and form the matrix in which the reinforcing fibres are embeddedin the desired configuration. Instead of fibres,thermoplastic films maybe used.

For advanced composites the use is desired of fibres from polymershaving a high thermal stability and a high strength. As a suitablepolymer may be mentioned, for instance, a wholly aromatic polyamide, andfor a reinforcing material the use is known of fibres of polyphenyleneterephthalamide. These fibres, however, are not thermoplastic belowtheir decomposition temperature and therefore not suitable for use asmatrix material. The older nonprepublished Patent application EP-A-239159 describes wholly aromatic copolyamides which are built up of atleast four different monomers, of which at least one is an aromaticamino carboxylic acid. These copolyamides, however, are difficult tospin into fibres.

The invention has for its object to provide a wholly aromaticcopolyamide which displays the chemical and thermal stability inherentin aromatic polyamides and moreover embodies thermoplasticity, ease ofspinning and a high heat distortion temperature desirable for acombination of reinforcing fibres and thermoplastic fibres suitable forforming a composite structure.

Accordingly, the invention provides a combination as described in claim1.

The copolyamides to be used according to the invention as thermoplasticfibres display a glass transition temperature above 200° C., preferablyabove 250° C., and a correspondingly high heat distortion temperature.The present copolyamides can be spun from the solution in which they areprepared. The present copolyamides are essentially amorphous and canmoreover be processed above their glass transition temperature while inthe thermoplastic state.

The present copolyamides are built up of at least four differentmonomers, of which at least two form an aromatic diamine and at leasttwo an aromatic dicarboxylic acid or dicarboxylic acid derivative. Thedivalent radicals linking the two amino groups or carbonyl groups arearomatic radicals in the sense that the amino nitrogen atoms or thecarbonyl carbon atoms are directly linked to an aromatic core. Thedivalent aromatic radicals are selected from the groups P1, P2, Q1 andQ2.

In the radicals selected from the groups P1 and P2 the two freevalencies are in the position para to each other, in the sense that theyare oriented parallel to each other or virtually co-axial. The sub-groupP1 comprises the radicals 1,4-phenylene, 1,5-naphthalene,2,6-naphthalene and 4,4'-biphenylene, in which the free valencies areoriented permanently parallel to each other. The sub-group P2 comprisesradicals with two aromatic rings linked by the group X, and the freevalencies can be positioned parallel to each other by rotation of thearyl-X-bonds.

The monomers which lead to the radicals from the group P1 are:1,4-diaminobenzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene,4,4'-diaminobiphenyl, 1,4-benzene dicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalene dicarboxylic acid and 4,4'-diphenyldicarboxylic acid and, for the polycondensation,use is generally made ofreactive derivatives of the dicarboxylic acids, more particularlydicarbonyl halides. The monomers selected from the group P2 are3-aminophenyl-4'-aminophenyl alkane-m,m, where the alkane may have 1 to9 carbon atoms and m represents an integer from 1-9, e.g.3-aminophenyl-4'-aminophenyl methane, or 3-aminophenyl-4'-aminophenylpropane-2,2, and3-aminophenyl-4'-aminophenyl-cyclohexane-1,1,3-aminophenyl-4'-aminophenylether, 3-aminophenyl-4'-aminophenyl sulphide,3-aminophenyl-4'-ainophenyl sulphone, and 3,4'-diaminobenzophenone, andthe corresponding dicarboxylic acid or dicarbonyl halides or otherreactive derivatives.

In the radicals from the groups Q1 and Q2 the two valences are in theposition meta to each other, in the sense that they are at an angle toeach other of about 120° C., more particularly between 105° C. and 130°C. The sub-group Q1 comprises the radicals 1,3-phenylene, 1,6- and1,7-naphthalene, 2,7-naphthalene and 2,4-naphthalene, in which the freevalencies are oriented rigid relative to each other and the anglebetween them is approximately 120° C. The sub-group Q2 comprisesradicals with two aromatic rings linked together by the group X, and thefree valencies are oriented to an angle between them of 90°-130°.

The monomers which lead to the radicals from the group Q1, are:1,3-diaminobenzene, 1,6-diaminonaphthalene, 2,7-diaminonaphthalene,3,4'-diaminobiphenyl, 1,3-benzene dicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 2,7-naphthalene dicarboxylic acid and 3,4'-biphenyldicarboxylic acid, and, for the polycondensation,use is generally madeof reactive derivatives of the dicarboxylic acids, more particularlydicarbonyl halides. The monomers from the group Q2 arebis-(3-aminophenyl)alkane-m,m and bis-(4-aminophenyl)alkane-m,m, wherethe alkane may have 1 to 9 carbon atoms and m represents an integer from1-9, e.g. bis(3-aminophenyl)methane, bis(4-aminophenyl)methane orbis(4-aminophenyl)propane-2,2, and bis(3- aminophenyl) cyclohexane-1,1,bis(4-aminophenyl)cyclohexane-1,1, bis(3-aminophenyl) ether,bis(4-aminophenyl)ether, bis(3-aminophenyl)sulphide,bis(4-aminophenyl)sulphide, bis(3-aminophenyl)sulphone,3,3'-diaminobenzophenone and 4,4'-diaminobenzophenone, and thecorresponding dicarboxylic acids and dicarbonyl halides or otherreactive derivatives.

The groups P1, P2, Q1 and Q2 also include the radicals which peraromatic ring comprise 1 to 4 inert substituents R, where R stands forC₁₋₄ -alkyl, e.g. methyl, C₁₋₄ -alkoxy, e.g. methoxy, Cl, F, aryl,ortho-fused benzono or aryl-C₁₋₄ -alkyl, e.g. benzyl. As examples ofsuch radicals may be mentioned 2-methoxy-1,4-phenylene (P1),2-methyl-1,4-phenylene (P1), 2-chloro-1,4-phenylene (P1),1,4-naphthylene (P1), 2,5-diphenylene (P1), 4-methyl-1,3-phenylene (Q1),5-methyl-1,3-phenylene (Q1), 2,4-diphenylene (Q1), 3,5-diphenylene (Q1),1,3-naphthylene (Q1), 3,3'-dimethoxybenzophenone4,4'-ylene (Q2), the4,4'-diradical of 1,2-dinaphthyl ether (P2) and the 4,4'-diradical of1,1'-dinaphthyl ether (Q2).

For thermoplasticity the present copolyamides comprising at least fourmonomer units cannot be composed in just any ratio. Based on the totalof amide bonds or monomer units the mole fraction for each of themonomer units must not be higher than 0.32. The proportion of radicalsfrom the groups P1 and P2 together must be in the range of 0.18 to 0.82.Likewise, the proportion of radicals from the groups Q1 and Q2 togethermust be in the range of 0.18 to 0.82, the proportion of radicals fromthe group Q2 being at least 0.15. In satisfying the requirements for theratios between the radicals from the groups P1, P2, Q1 and Q2 it doesnot make any difference whether the radical is from a diamine or from adicarboxylic acid.

It is preferred that in either case the proportion of radicals from thegroups P1 and P2 and Q1 and Q2 should be in the range of 0.36 to 0.74.

It is preferred that the present copolyamide should be built up ofexactly four monomers, viz. two dicarboxylic acids and two diamines.Said requirements are met in that case if at least one monomer comprisesa radical from the groups P1 and P2, and at least one monomer comprisesa radical from the group Q2.

The most suitable are copolyamides built up of predominantly equimolaramounts (0.22-0.28) of 4 monomer units derived from para- ormeta-oriented diamines and dicarboxylic acids, with the ratio betweenthe amine groups and the acid groups being of course virtuallystoichiometric.

The present copolyamides may be prepared in the usual manner, forinstance by melt polymerization, solid phase polymerization, interfacialpolymerization or solution polymerization. It is preferred that thepolymerization should be carried out in a solvent system which containsat least a solvent of the amide type, such as N-methyl-2-pyrrolidone,N,N-dimethyl acetamide, tetramethyl urea, or a mixture thereof.Optionally, the solvent system may contain a solubility enhancing salt,more particularly an alkali or earth alkali halide, such as lithiumchloride or calcium chloride. In solution polymerization thedicarboxylic acids are preferably used in the form of their acidchlorides and added with vigorous stirring to, for instance, a cooledsolution of the diamines. The amide solvent also serves as acid acceptorfor the hydrogen chloride evolved in the polycondensation.

Depending on the concentration of the polymerizable constituents, thedegree of polymerization to be attained, the nature of the solvent, thenature of the monomer units and the final temperature of thepolycondensate, generally a solution of the copolyamide will beobtained. If the addition of a solubility enhancing salt is required,then an (earth) alkali hydroxide, (earth) alkali oxide, (earth) alkalicarbonate, such as lithium carbonate or calcium hydroxide may be addedwhich acts as an acid acceptor, as a result of which the envisagedlithium chloride or calcium chloride is formed in situ.

The advantage to the present copolyamides is that they are soluble inthe polycondensation medium. The resulting solutions can be directlyspun by coagulation of the polycondensate solution passing from aspinneret into a spinning bath containing water or a mixture of waterand amide solvent. If necessary, the viscosity of the polycondensatesolution may be adjusted or the conditions of the polycondensation beset to the optimum value for spinning, preferably without using asolubility enhancing (earth) alkali halide in order to avoid theattendant need for washing it out. Setting the viscosity to the desiredvalue falls within the reach of the person of ordinary skill in the art.

The concentration of polymerizable constituents in the polycondensationmixture is generally in the range of 5 to 25% by weight, thepolycondensation being carried out at a temperature in the range of -20°C. to 100° C. In this way fibres or films having a thickness between 5and 200 μm are obtained.

By fibres according to the invention are also to be understood fibrilsobtained by pouring a copolyamide solution into a vigorously stirredcoagulation liquid.

The fibres or films from the present aromatic copolyamide along withreinforcing fibres may be formed into a combination according to theinvention by any known method. By combination is to be understood hereany more or less coherent mixed structure of types of fibres or films,more particularly a flexible textile product which contains a blend ofthe two types of material and is sufficiently flexible to be rolled upfor storage or be formed into the desired final shape. As examples ofsuch structures may be mentioned rovings, fibre tows, yarns, fabrics,nettings, knittings, webs and fleeces of reinforcing fibres andthermoplastic fibres, and laminates of thermoplastic films and fabricsor fleeces of reinforcing fibres. Examples of the combinations referredto above are described in DE-A-34,08 769 and EP-A-156 600.

The reinforcing fibres and the thermoplastic fibres may be blendedhomogeneously or inhomogeneously to a specific extent in accordance withknown technique, after which the blended yarns obtained are formed intosome textile structure. Alternatively, the two types of yarns may beseparately fed in the process of manufacturing the textile structure,for instance to form the warp and weft in a fabric. For woven fabricsuse is preferably made of endless fibres or yarns, whereas staple fibresmay be effectively processed into non-woven fleeces.

The reinforcing fibres to be used for the combination according to theinvention are known and commonly used for the reinforcement of plastics,be it that reinforcing materials which melt, soften or decompose below400° C. are not suitable for this purpose. As examples of suitablereinforcing materials may be mentioned glass fibres, carbon fibres,metallic fibres, ceramic fibres, boron fibres and fibres of some organicpolymers displaying high strength and high thermal stability, such aspolyaramid and polyimide, viz. polyparaphenylene terephthalate,poly-p-phenylene benzobisoxazole or poly-p-phenylene benzobisthiazole.Alternatively, combinations of reinforcing fibres may be used.

Good results have been obtained with a combination in which use is madeof reinforcing fibres coated with a solution of the amorphouscopolyamide.

The combination according to the invention serving as semi-manufacturedproduct is generally subjected to compression moulding, which is carriedout, if desired, under vacuum or an inert atmosphere. The mouldingpressure may be in the range of 0.5 to 1000 bar or higher. Thetemperature used is between the glass transition temperature of thecopolyamide and an upper limit depending on the technology used, whichin practice is in the range of 300° C. to 400° C. Or the temperaturesand/or pressures may be varied stepwise or in some places a deviatingpressure/temperature may be used for special effects.

Textile hose, belts, strips and fibre bundles containing the presentcopolyamide in combination with reinforcing fibres may be subjected to acontinuous compression moulding process, preferably while using sometensile stress. Thus it is possible in a simple manner to manufactureunidirectionally reinforced continuous sections, e.g. round or angularbars, tubes and tapes.

Unidirectionally reinforced tapes of a thickness permitting sufficientflexibility are not only of importance as endproduct having a very hightensile strength in longitudinal direction, but also constitute asuitable semi-manufacture for the manufacture of advanced compositestructures. When such tapes are wound under tensile tension and at amelting temperature, the resulting structures may display excellentmechanical properties. Also because of the excellent thermal andchemical resistance of the present copolyamides, these compositescompare favourably with the known plastics structures, so that they mayfind application in fields where metal and ceramic materials have so farbeen found irreplaceable and advantage may be taken of theirconsiderably lower weight.

The invention will be further described in the following examples.

EXAMPLE I A. Preparation of copolyamide

90.1 g of paraphenylene diamine (PPD: 0.834 moles) and 165.2 g ofbis(4-aminophenyl) methane (MDA; 0.834 moles) were dissolved in 3000 mlof N-methyl-2-pyrrolidone (water content about 0.03%). A mixture of169.25 g of terephthaloyl dichloride (TDC; 0.834 moles) and 172.70 g ofisophthaloyl dichloride (IDC; 98% purity; 0.834 moles) was added withvigorous stirring at a temperature of 22° C. After continued stirringfor 1.5 hours a solution of 13.5% by weight of copolyamide PPD/MDA/TDC/IDC (1:1:1) was obtained. The viscosity of this solution was 280Pa.s at 25° C. The relative viscosity n_(rel) of the copolyamide was2,97 (0.5 g in 100 ml of H₂ SO₄ at 25° C.).

B1. Spinning of filaments

The solution of the copolyamide obtained under A was filtered, degassedand extruded at a nitrogen pressure of 2-4 bar and at a speed of 23.3m/min through a spinneret having 100 orifices 0.06 mm in diameter eachimmersed in a water bath of 20° C. The filaments obtained were washedwith water of 70° C. and wound at a speed of 7 m/min. The properties ofthe resulting yarn were as follows:

    ______________________________________                                        tenacity:              117 MPa                                                elongation:            25%                                                    modulus of elasticity: 4.4 GPa                                                ______________________________________                                    

B2. Spinning of film

A copolyamide solution obtained as described under A was extruded into awater bath of 20° C. through a spinneret having a slit measuring 20mm×0.1 mm. The outflow opening of the spinneret and the surface of thecoagulation bath was separated by an air gap of 20 mm. The coagulate waswithdrawn from the water bath at a rate of 4.6 m/min; washed with hotwater and wound up. The resulting film had a width of about 8 mm and athickness of 0.1 mm.

C. Compression moulding

A 10-layer bundle of the film obtained under B2 was placed in a fittingmould measuring 100 mm×50 mm×0.8 mm.

The mould consisted of three layers of aluminium foil 0.8 mm thick, themiddle layer having a hole measuring 100×50 mm.

The whole was heated for 1.5 min at a pressure of 10 bar in a presspreheated to 350° C. and 380° C., respectively. Subsequently, pressurewas applied for 4.5 minutes, followed by cooling for 6 minutes at apressure of 10 bar. At both pressure temperatures a homogeneous, clear,pale yellow strip 0.8 mm thick was obtained.

Use being made of the same procedure, a combination of a plain fabric ofaramid yarn (under the trade mark Twaron) provided on either side with afive-layer bundle of the strip obtained under B2 was subjected tocompression moulding, resulting in a void-free composite structurecomprising the present amorphous copolyamide as matrix and the aramidfabric as reinforcing structure.

EXAMPLE II

Use being made of the same procedure as given in Example I, acopolyamide was prepared from

25.00 moles of paraphenylene diamine

25.00 moles of bis(4-aminophenyl)methane

25.05 moles of terephthaloyl dichloride and

25.05 moles of isophthaloyl dichloride.

The polymerization was carried out in N-methyl-2-pyrrolidone at amonomer concentration of 16.6% by weight. Upon conclusion of thereaction a polymer solution was obtained having a polymer concentrationof 12,4% by weight. Through this solution there was passed apolyparaphenylene terephthalamide yarn having a linear density of dtex1759. The yarn had the following properties:

    ______________________________________                                        tenacity:             1924 mN/tex                                             elongation at rupture:                                                                              3.47%                                                   modulus:              69.6 GPa                                                ______________________________________                                    

This polyaramid yarn was passed through a bath containing the abovepolymer solution at a rate of 5 m/minute, and subsequently through a hotwater bath for further coagulation of the solution applied to it andremoval of the solvent. After having been afterwashed for 16 hours, theyarns were dried to the air.

The resulting polyaramid yarn coated with amorphous polyaramid wasblended with copolyamide filaments of Example I B1 until a volume ratiobetween polyparaphenylene terephthalamide yarn and copolyaramid of 1:1was obtained. The composition thus obtained was heated to 380° C. in amould 10 mm wide and 2.50 mm thick and subsequently compression mouldedat said temperature and at a pressure of 10 bar into a void-freestructure. After the resulting composite had been cooled to roomtemperature, it was subjected to a measurement with Instron 1026 tensiletester at a temperature of 21° C. and at a rate of 2.0 mm per minute, bywhich it was found to have the following properties:

    ______________________________________                                        flexural modulus:                                                                             30847 MPa                                                     flexural stress 1.5 h:                                                                        488.4 MPa                                                     flexural stress at max. load:                                                                 491.3 MPa                                                     elongation at rupture                                                                         3.7%                                                          offset yield 0.1%                                                                             331.4 MPa at an elongation of 1.2%                            offset yield 1.0%                                                                             474.7 MPa at an elongation of 2.6%                            ______________________________________                                    

I claim:
 1. A copolyamide, which expressed as the mole fraction of thetotal of amide bonds, comprises: (1) 0.22-0.28 units derived fromterephatalic acid; (2) 0.22-0.28 units derived from paraphenylenediamine; (3) 0.22-0.28 units derived from isophthalic acid; and (4)0.22-0.28 units derived from a 3,3'- or a 4,4'-diamine of diphenylmethane, diphenylpropane-2,2, diphenyl cyclohexane-1,1, diphenyl ether,diphenyl sulfide, diphenyl sulphone, or benzophenone.
 2. A copolyamideas claimed in claim 1 wherein the last recited unit is derived from a3,3'-diamine of diphenyl methane.
 3. A copolyamide as claimed in claim 1wherein the last recited unit is derived from a 4,4'-diamine of diphenylmethane.
 4. A copolyamide as claimed in claim 1 wherein the last recitedunit is derived from a 3,3'-diamine of diphenylpropane-2,2.
 5. Acopolyamide as claimed in claim 1 wherein the last recited unit isderived from a 4,4'-diamine of diphenylpropane-2,2.
 6. A copolyamide asclaimed in claim 1 wherein the last recited unit is derived from a3,3'-diamine of diphenyl cyclohexane-1,1.
 7. A copolyamide as claimed inclaim 1 wherein the last recited unit is derived from a 4,4'-diamine ofdiphenyl cyclohexane-1,1.
 8. A copolyamide as claimed in claim 1 whereinthe last recited unit is derived from a 3,3'-diamine of diphenyl ether.9. A copolyamide as claimed in claim 1 wherein the last recited unit isderived from a 4,4'-diamine of diphenyl ether.
 10. A copolyamide asclaimed in claim 1 wherein the last recited unit is derived from a3,3'-diamine of diphenyl sulphide.
 11. A copolyamide as claimed in claim1 wherein the last recited unit is derived from a 4,4'-diamine ofdiphenyl sulphide.
 12. A copolyamide as claimed in claim 1 wherein thelast recited unit is derived from a 3,3'-diamine of diphenyl sulfone.13. A copolyamide as claimed in claim 1 wherein the last recited unit isderived from a 4,4'-diamine of diphenyl sulfone.
 14. A copolyamide asclaimed in claim 1 wherein the last recited unit is derived from a3,3'-diamine of diphenyl benzophenone.
 15. A copolyamide as claimed inclaim 1 wherein the last recited unit is derived from a 4,4'-diamine ofdiphenyl benzophenone.